Du Xing, Nagata Satoshi, Ise Tomoko, Stetler-Stevenson Maryalice, Pastan Ira
Laboratory of Molecular Biology, Center for Cancer Research, National Cancer Institute, National Institutes of Health, Bethesda, MD 20892-4264, USA.
Blood. 2008 Jan 1;111(1):338-43. doi: 10.1182/blood-2007-07-102350. Epub 2007 Sep 25.
FCRL1 (Fc receptor-like 1) is a cell-surface membrane protein belonging to FCRL family and is preferentially expressed on B cells. To evaluate FcRL1 as an immunotherapy target for B-cell malignancies, we prepared anti-FCRL1 mAbs without cross-reactivity to other FCRL family proteins and analyzed FCRL1 protein expression on malignant cells from patients and on B-cell lines. Frequent FCRL1 expression was observed by flow cytometry on 12 B-cell non-Hodgkin lymphoma (B-NHL) cell lines and many patient samples: 12 of 14 chronic lymphocytic leukemia (CLL), 7 of 7 follicular lymphoma (FL), 13 of 17 hairy cell leukemia (HCL), and 2 of 3 mantle cell lymphoma (MCL). Two recombinant immunotoxins, E3(Fv)-PE38 and E9(Fv)-PE38, were constructed. Both immunotoxins bound to FCRL1-positive cells with similar affinities (3.4 and 3.2 nM) and were cytotoxic to cell lines, but E9(Fv)-PE38 was 4- to 20-fold more cytotoxic than E3(Fv)-PE38. The concentrations that inhibited response by 50% (IC(50)s) of E9(Fv)-PE38 on 11 different FCRL1-positive cell lines ranged from 1.0 ng/mL to 90 ng/mL and correlated with the FCRL1 expression levels. Our results suggest that anti-FCRL1 immunotoxin E9(Fv)-PE38 exhibits remarkably specific cytotoxicity and merits further evaluation for the treatment of FCRL1-positive malignancies, including CLL, HCL, FL, MCL, and other B-NHL.
FCRL1（Fc受体样蛋白1）是一种属于FCRL家族的细胞表面膜蛋白，优先表达于B细胞。为了评估FcRL1作为B细胞恶性肿瘤的免疫治疗靶点，我们制备了与其他FCRL家族蛋白无交叉反应的抗FCRL1单克隆抗体，并分析了患者恶性细胞和B细胞系上FCRL1蛋白的表达。通过流式细胞术在12种B细胞非霍奇金淋巴瘤（B-NHL）细胞系和许多患者样本中观察到FCRL1的频繁表达：14例慢性淋巴细胞白血病（CLL）中有12例，7例滤泡性淋巴瘤（FL）中的7例，17例毛细胞白血病（HCL）中的13例，以及3例套细胞淋巴瘤（MCL）中的2例。构建了两种重组免疫毒素E3(Fv)-PE38和E9(Fv)-PE38。两种免疫毒素以相似的亲和力（3.4和3.2 nM）与FCRL1阳性细胞结合，并对细胞系具有细胞毒性，但E9(Fv)-PE38的细胞毒性比E3(Fv)-PE38高4至20倍。E9(Fv)-PE38对11种不同FCRL1阳性细胞系的50%抑制反应浓度（IC50）范围为1.0 ng/mL至90 ng/mL，并与FCRL1表达水平相关。我们的结果表明，抗FCRL1免疫毒素E9(Fv)-PE38表现出显著的特异性细胞毒性，值得进一步评估用于治疗FCRL1阳性恶性肿瘤，包括CLL、HCL、FL、MCL和其他B-NHL。
